<cn>
#### 动态增减表单项
动态增加、减少表单项。
</cn>

<us>
#### Dynamic Form Item
Add or remove form items dynamically.
</us>


<template>
<a-form @submit="handleSubmit" :form="form">
  <a-form-item
    v-for="(k, index) in form.getFieldValue('keys')"
    v-bind="index === 0 ? formItemLayout : formItemLayoutWithOutLabel"
    :label="index === 0 ? 'Passengers' : ''"
    :required="false"
    :key="k"
  >
    <a-input
      v-decorator="[
        `names[${k}]`,
        {
          validateTrigger: ['change', 'blur'],
          preserve: true,
          rules: [{
            required: true,
            whitespace: true,
            message: 'Please input passenger\'s name or delete this field.',
          }],
        }
      ]"
      placeholder='passenger name'
      style="width: 60%; margin-right: 8px"
    />
    <a-icon
      v-if="form.getFieldValue('keys').length > 1"
      class='dynamic-delete-button'
      type='minus-circle-o'
      :disabled="form.getFieldValue('keys').length === 1"
      @click="() => remove(k)"
    />
  </a-form-item>
  <a-form-item v-bind="formItemLayoutWithOutLabel">
    <a-button type='dashed' @click="add" style="width: 60%">
      <a-icon type='plus' /> Add field
    </a-button>
  </a-form-item>
  <a-form-item v-bind="formItemLayoutWithOutLabel">
    <a-button type='primary' htmlType='submit'>Submit</a-button>
  </a-form-item>
</a-form>
</template>

<script>
let id = 0;
export default {
  beforeCreate () {
    this.form = this.$form.createForm(this);
    this.form.getFieldDecorator('keys', { initialValue: [] });
  },
  data () {
    return {
      formItemLayout: {
        labelCol: {
          xs: { span: 24 },
          sm: { span: 4 },
        },
        wrapperCol: {
          xs: { span: 24 },
          sm: { span: 20 },
        },
      },
      formItemLayoutWithOutLabel: {
        wrapperCol: {
          xs: { span: 24, offset: 0 },
          sm: { span: 20, offset: 4 },
        },
      },
    };
  },
  methods: {
    remove  (k) {
      const { form } = this;
      // can use data-binding to get
      const keys = form.getFieldValue('keys');
      // We need at least one passenger
      if (keys.length === 1) {
        return;
      }

      // can use data-binding to set
      form.setFieldsValue({
        keys: keys.filter(key => key !== k),
      });
    },

    add  () {
      const { form } = this;
      // can use data-binding to get
      const keys = form.getFieldValue('keys');
      const nextKeys = keys.concat(++id);
      // can use data-binding to set
      // important! notify form to detect changes
      form.setFieldsValue({
        keys: nextKeys,
      });
    },

    handleSubmit  (e) {
      e.preventDefault();
      this.form.validateFields((err, values) => {
        if (!err) {
          console.log('Received values of form: ', values);
        }
      });
    },
  },
};
</script>
<style>
.dynamic-delete-button {
  cursor: pointer;
  position: relative;
  top: 4px;
  font-size: 24px;
  color: #999;
  transition: all .3s;
}
.dynamic-delete-button:hover {
  color: #777;
}
.dynamic-delete-button[disabled] {
  cursor: not-allowed;
  opacity: 0.5;
}
</style>





